This applicant has already provided with a main shaft device for machine tools that a mist feed tube for feeding cutting fluid mists from the rear side of a main shaft to the front side thereof is disposed in the rotation center of the main shaft driven for rotation, and the front of the mist feed tube is inserted into the rotation center of a tool holder fixed to the front of the main shaft to ensure that the cutting fluid mists flowing out of the front end of the mist feed tube spout from the front end of a cutting tool fixed to a tool holder via a mist passageway in the rotation center of the tool holder and via a mist hole of a cutting tool fixed to the tool holder.
The above-mentioned main shaft device is generally provided with a marketable cutting tool. The caliber of a mist hole is suitably decided in accordance with the outer diameter and the length of a cutting tool body, a form of cutting tool or cutting tool maker's own peculiar reasons. Generally, the caliber is about as large as size to pass sufficient cutting fluid mists in various machining by the cutting tool.
The above-mentioned main shaft device has enough capacity for feeding the cutting fluid mists by the mist feed tube in general machining. Accordingly, the cutting fluid mists flowing out of the mist feed tube spout from the front end surface of the cutting tool in the flow rate depending on the caliber or the length of the mist hole of the cutting tool.
Therefore, in almost practical machining, too many cutting fluid mists spout from the front end surface of the cutting tool, thereby causing the wasting of cutting fluid mists and contamination of a machining environment with cutting fluid mists.
The present invention aims to provide a main shaft device for machine tools that can settle the above problems.